Mechanical effects of optical vortices
N. R. Heckenberg, M. E. J. Friese, T. A. Nieminen, H. Rubinsztein-Dunlop
我们专注于力和扭矩施加在透明和吸收粒子被困在激光束中包含光学涡旋。我们回顾了以前的理论和实验工作，然后提出了新的计算涡旋光束的效果吸收粒子。
We concentrate on the forces and torques exerted on transparent and absorbing particles trapped in laser beams containing optical vortices. We review previous theoretical and experimental work and then present new calculations of the effect of vortex beams on absorbing particles.
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Topology of Knotted Optical Vortices
光学涡旋作为一种拓扑对象在自然界中普遍存在。本文利用$ϕ$ -映射拓扑流理论，研究了封闭和打结光学涡旋中的拓扑结构。得到了光学涡旋的拓扑内部结构，并给出了纽结光学涡旋的连接。
Stable higher-charge discrete vortices in hexagonal optical lattices
我们发现，在单电荷涡旋总是表现出动力学不稳定性的六边形光子晶格中，双电荷离散光学涡旋可能是完全稳定的。即使在不稳定时，双电荷涡旋通常也比单电荷涡旋具有更弱的不稳定性，因此它们的分裂发生在更长的传播距离处。
Polygonal Spatiotemporal Optical Vortices Wavepackets with Prescribed Vortex Structure
本文提出并实验展示了具有预设涡旋结构的多边形时空光涡波包，通过时空全息成形方法实现对光涡几何和分布的精确控制。
We investigate the dynamic behavior of optical vortices, or phase singularities, in random wavefields and demonstrate the direct experimental observation of the anomalous diffusion of optical vortices. The observed subdiffusion of optical vortices show excellent agreement with the fractional Brownian motion, a Gaussian process. Paradoxically, the vortex displacements are observed exhibiting a non-Gaussian heavy-tailed distribution. We also tune the extent of subdiffusion and non-Gaussianity of optical vortex by varying the viscoelasticity of light scattering media. This complex motion of optic…
We exploit the vorticity, familiar from fluid mechanics and the theory of superfluids, as a tool to track the birth and subsequent development of optical vortices at a spiral phase plate.
Measuring the positions of optical vortices is an essential part in the researches of speckles and adaptive optics. The measurement accuracy is restricted by the performance of optical devices and the properties of optical vortices, such as density and size. In order to achieve high accuracy and wide range of application, the dual shearing-type Sagnac interferometers is proposed using two shearing plates to adjust the precision of optical vortices measurement. The shearing displacements are able to balance the measuring precision and the value of the intensity ratio point to provide optimum me…
We harness the momentum of light resonating inside a micro-droplet cavity, to experimentally generate micro-flows within the envelope of the drop. We 3D map these optically induced flows by using fluorescent nanoparticles; which reveals circular micro-streams. The flows are parametrically studied and, as expected, exhibit an increase of rotation speed with optical power. The flow is non-circular only when we intentionally break the axial symmetry of the droplet. Besides the fundamental interest in light-flow interactions including in opto-fluidic cavities, the optically controlled flows can se…
Optical vortices are the electromagnetic analogue of fluid vortices studied in hydrodynamics. In both cases the traveling wavefront, either made of light or fluid, is twisted like a corkscrew around its propagation axis - an analogy that inspired also the first proposition of the concept of optical vortex. Even though vortices are one of the most fundamental topological excitations in nature, they are rarely found in their electromagnetic form in natural systems, for the exception of energetic sources in astronomy, such as pulsars, quasars and black holes. Mostly optical vortices are artificia…
We report on the generation of high-order optical vortices by spiral phase mirrors. The phase mirrors are produced by direct machining with a diamond tool and are shown to produce high-quality optical vortices with topological charges ranging from 1 to 1000 at a wavelength of 532 nm. The direct machining technique is flexible and offers the promise of high-precision, large-diameter spiral phase mirrors that are compatible with high optical powers.
In optics, we can generate vortex beams using specific methods such as spiral phase plates or computer generated holograms. While, in nature, it is worth noting that water can produce vortices by a circularly symmetrical hole. So, if a light beam can generate vortex when it is diffracted by an aperture? Here, we show that the light field in the Fresnel region of the diffracted circularly polarized beam carries orbital angular momentum, which can transfer to the trapped particles and make orbital rotation.
We present the dynamics of optical vortices (OVs) that came from the propagation of helico-conical optical beam. This dynamics is investigated numerically by tracking the OVs at several distances using rigorous scalar diffraction theory. To ensure that our numerical calculations are correct, we compare the intensity profiles and their corresponding interferograms taken at different propagation distances between simulations and experiments. We observe that the peripheral isopolar vortices transport radially inward, toward the optical axis along the transverse spatial space as the beam propagate…
Orbital angular momentum of spatiotemporal vortices: a ray-mechanical analogy
本文通过机械模型类比，揭示了时空涡旋脉冲的轨道角动量特性，通过非均匀质量分布和半经典涡旋量化条件，实现了对近轴STVPs的OAM结果的精确再现。
We have experimentally generated higher order optical vortices and scattered them through a ground glass plate that results in speckle formation. Intensity autocorrelation measurements of speckles show that their size decreases with increase in the order of the vortex. It implies increase in angular diameter of the vortices with their order. The characterization of vortices in terms of their annular bright ring also helps us to understand these observations. The results may find applications in stellar intensity interferometry and thermal ghost imaging.
We investigate the propagation properties of the optical vortices emitted from a collectively polarized electric dipole array as a simple model of the several emitters. Using an analytical approach based on the Jacobi-Anger expansion, we derive a relationship between the topological charge of the optical vortices and the source conditions of the emitter, and clarify and report our new finding; there exists an intrinsic split of the singular points in the electric field due to the spin-orbit interaction of the dipole fields.
We show that a two-dimensional hydrodynamics model provides a physical explanation for the splitting of higher-charge optical vortices under elliptical deformations. The model is applicable to laser light and quantum fluids alike. The study delineates vortex breakups from vortex unions under different forms of asymmetry in the beam, and it is also applied to explain the motion of intact higher-charge vortices.
Quadrefringence of optical vortices in a uniaxial crystal
本文从理论和实验上描述了光斜通过单轴晶体时，单个光涡旋分裂成四个独立的光涡旋。我们还发现了在任何晶体长度下，每四个单独光束中的新生涡旋独立传播而没有位错反应，并且在所有光束中具有不同位置的条件。
Rotationally induced vortices in optical cavity modes
我们表明，涡旋出现在模式的旋光腔时，它是投入到旋转其光轴。我们研究这些旋涡的性质，并讨论数值结果的具体实现这样一个设置。我们的方法是准确的，直到一阶的依赖于时间的傍轴近似，并涉及玻色子阶梯运营商的量子力学谐振子的精神。
We propose to generate optical vortices using a degenerate optical resonator with an intra-cavity spiral phase plate (SPP). The rays retracing skewed V-shaped paths in the resonator are phase-locked to form vortex laser with wavefront dislocation mirroring the topological charge of the SPP. Experimental demonstrations on diode-pumped solid state system using Nd:YAG crystal emitted randomly polarized optical vortices at a wavelength of 1064nm when the pump power went above 1.52W and the slope efficiency was 0.19. For long-term operations a power fluctuation of 2.2\% and pointing stability of 2.…
Mode purity is an important reference for the quality of the optical vortex. In this work, we propose a self-interference method to directly measure single component in superposed optical vortices based on phase-shifting technology. This method has excellent flexibility and robustness, which can be applied to a variety of occasions and harsh conditions. Careful alignment and optimized error analysis allow us to generate and measure single component with mode purity as high as 99.997%.
Mesh of Spatiotemporal Optical Vortices with Programmable Intensity Nulls
本研究提出并实验验证了具有可编程强度零点的二维时空光学涡旋网格，扩展了其频谱范围并分析了OAM传递。
Spatiotemporal optical vortices (STOVs) are a new type of intrinsic optical orbital angular momentum (OAM) structure in which the OAM vector is orthogonal to the propagation direction [Optica 6, 1547, (2019)] and the optical phase circulates in space-time. Here, we experimentally and theoretically demonstrate, for the first time, the generation of the second harmonic of a STOV-carrying pulse along with the conservation of STOV-based OAM. Our experiments verify that individual photons can have intrinsic orbital angular momentum perpendicular to their propagation direction.
In this work, an analytic expression is derived for the optical field generated by an off-axis Gaussian beam diffracted by a Discrete Vortex-Producing Lens. With this system, a multifocal arrangement of asymmetric optical vortices is obtained whose topological charge values change with the position along the optical axis. This scheme allows obtaining a principal asymmetric vortex corresponding with the topological charge value of the phase mask and secondary ones with different charges. With the analytical expression, the effects induced by the discretization and misalignment on the irradiance…
Coherent beam combining of optical vortices
本研究基于掺镱光纤短脉冲激光系统，通过相干光束合成实现了l=1到l=5拓扑荷数光学涡旋的功率定标，合成效率达83.2%-96.9%，为高强度光学涡旋的科学与工业应用开辟了新路径。
We show that double-charged optical vortices can be generated with the help of Kerr electrooptic effect in either single crystals or isotropic media, including gaseous and liquid ones. We analyze possibilities for the vortex generation via the Kerr effect for different point group of symmetry and formulate the appropriate conditions. We prove that the crystals, textures and the isotropic media most suitable for the generation of double-charged optical vortices should belong to the symmetry groups 622, 6mm, 6/mmm, 6, 6/m, inf/m, inf, inf 2, inf mm, inf/mmm, inf/inf/mmm, and inf/inf2.
In this study, we demonstrate the concept of combining optical combs with optical vortices for the first time. By combining the advantages of the both light sources, we realize an optical vortex comb technology for arbitrary spatiotemporal phase manipulation. This idea corresponds to simultaneous control of the longitudinal and transverse modes of light based on the high controllability of the optical comb. As a proof-of-concept experiment, we applied an optical vortex comb to the generation and rotational control of a ring-shaped optical lattice. Furthermore, to demonstrate the utility of thi…
We study Mie scattering of Laguerre-Gaussian (LG) light beams remodelled using the method of far-field matching. The theoretical results are used to analyze the optical field in the near-field region for purely azimuthal LG beams characterized by a nonzero azimuthal mode number $m_{LG}$. The mode number $m_{LG}$ is found to have a profound effect on the morphology of photonic nanojets and the near-field structure of optical vortices associated with the components of the electric field.
Self-reference interferometry of optical vortices using a Michelson interferometer is investigated in this paper. It is found that the detection of topological charge (TC) for the optical vortices is constrained by some physical conditions. We present these conditions through the theoretical analyses, numerical simulation and experimental results. For different parameters, the maximal detectable TCs are different, which is helpful for the measurement of TC in the practical application. Within the range allowed by the constrained conditions, we also study the detection of TC using the interfere…
Towards High-Energy Few-Cycle Optical Vortices with Minimized Topological Charge Dispersion
本文提出利用OPCPA的固有特性，在特定条件下将拓扑荷从高能窄带泵浦脉冲干净转移至宽带闲频光，从而生成具有极低拓扑荷色散的高能少周期光学涡旋。
Amplitude Structure of Optical Vortices Determines Annihilation Dynamics
本文研究光涡旋对的湮灭动力学，发现涡旋核初始尺寸可操控湮灭过程，流体动力学主导运动，减小核尺寸可阻止湮灭。
Perfect Spatiotemporal Optical Vortices
针对时空光学涡旋空间时间维度受拓扑荷限制的问题，提出完美时空光学涡旋，其直径与拓扑荷无关，并实现涡旋晶格的灵活操控。
The orbital angular momentum (OAM) of light holds great promise for applications in optical communication, super-resolution imaging, and high-dimensional quantum computing. However, the spatio-temporal coherence of the light source has been essential for generating OAM beams, as incoherent ambient light would result in polychromatic and obscured OAM beams in the visible spectrum. Here, we extend the applications of OAM to ambient lighting conditions. By miniaturizing spiral phase plates and integrating them with structural color filters, we achieve spatio-temporal coherence using only an incoh…
Recently, a spatiotemporal optical vortex (STOV) with a transverse orbital angular momentum (OAM) has been generated from coherent ultrafast pulses using mode-locked lasers. In contrast, we demonstrate theoretically and experimentally that a STOV can be generated from a light source with partial temporal coherence with fluctuating temporal phase. By eliminating the need of mode-locked laser sources, the partially coherent STOV will serve as a convenient and cost-effective transverse OAM source.
We consider the problem of singular beams in optics as a part of the general questions of interactions, shaping and transformations of vortex states with fractional topological charges in physics, in particular, in hydrodynamic and quantum mechanic. Starting from the representation of the fractional-order vortex states as a superposition of infinite number of integer-order vortices with distinctive energy distributions (the vortex spectra) we showed that the smooth wave front of the fractional vortex beam can either decay into an asymmetric array of integer-order vortices or, vice versa, the a…
Spatio-temporal optical vortices (STOVs) are a new type of optical orbital angular momentum (OAM) with optical phase circulation in space-time. In prior work [N. Jhajj et al., Phys. Rev X 6, 031037 (2016)], we demonstrated that a STOV is a universal structure emerging from the arrest of self-focusing collapse leading to nonlinear self-guiding in material media. Here, we demonstrate linear generation and propagation in free space of STOV-carrying pulses. Our measurements and simulations demonstrate STOV mediation of space-time energy flow within the pulse and conservation of OAM in space-time. …
The optical Talbot interferometer has been used to explore the topological charges of optical vortices. We recorded the self-imaging of a diffraction grating in the near-field regime with the optical vortex of several topological charges. Our twisted light was generated by a spatial light modulator (SLM). Previous studies showed that interferometric methods can determine the particular orbital angular momentum (OAM) states, but a large number of OAM eigenvalues are difficult to distinguish from the interference patterns. Here, we show that the Talbot patterns can distinguish the charges as wel…
Closed forms for spatiotemporal optical vortices and sagittal skyrmionic pulses
本文针对时空光学涡旋（STOVs），通过微分算子作用于复焦点脉冲推导出严格满足麦克斯韦方程组的解析表达式，并利用射线图像解释传播变形，最终提出覆盖所有横向偏振态的矢状面斯格明子脉冲。
Optical Vortices during a Super-Resolution Process in a Metamaterial
我们表明，具有100%可见度的超分辨率过程的特征在于在透镜外的自由空间中形成一个拓扑电荷等于-1的鞍形的相位奇点。鞍点连接到透镜的端部边界处的两个涡旋，并且这两个涡旋又连接到透镜内部的另一个鞍点。鞍涡鞍结构是拓扑稳定的。自由空间中鞍点的形成也解释了透镜外某个空间区域中存在的负能量通量。功率流的循环强度可以通过改变物平面相对于透镜的位置来控制。
The orbital angular momentum (OAM) of light has recently attracted a growing interest as a new degree of freedom in order to increase the information capacity of today optical networks both for free-space and optical fiber transmission. Here we present our work of design, fabrication and optical characterization of diffractive optical elements for compact OAM-mode division demultiplexing based on optical transformations. Samples have been fabricated with 3D high-resolution electron beam lithography on polymethylmethacrylate (PMMA) resist layer spun over a glass substrate. Their high compactnes…
Rows of optical vortices from elliptically perturbing a high-order beam
在高阶光束的光轴上存在一个具有高拓扑强度的光学涡旋（相位奇点）。椭圆扰动下的分裂成一个直排的单位强度的涡涡描述。研究了螺旋状Ince-Gauss光束和拉盖尔-高斯光束的微扰，即广义厄米-拉盖尔-高斯光束。这些光束的近似推导出小扰动，其中的轴的邻域可以近似由多项式在复平面：切比雪夫多项式的因斯-高斯光束，和厄米多项式的双折射光束。
Conservation of transverse orbital angular momentum for spatiotemporal optical vortices
本文通过去除窄带和近轴假设，证明了时空光学涡旋的横向轨道角动量在传播过程中保持守恒。
We present the first experimental evidence, supported by theory and simulation, of spatiotemporal optical vortices (STOVs). Quantized STOVs are a fundamental element of the nonlinear collapse and subsequent propagation of short optical pulses in material media. A STOV consists of a ring-shaped null in the electromagnetic field about which the phase is spiral, forming a dynamic torus which is concentric with and tracks the propagating pulse. Depending on the sign of the material dispersion, the local electromagnetic energy flow is saddle or spiral about the STOV. STOVs are born and evolve conse…
We have considered the paraxial vector erf-Gaussian beams with field distribution in the form of the error function that are shaped by the cone of plane waves with a fractional step of the azimuthal phase distribution modulated by the Gaussian envelope. We have revealed that the initial distributions of the transverse electric and transverse magnetic fields have the form far from standard ones but at the far diffraction field the field distributions recover nearly the symmetric form. We have also revealed that the half-charged vortices in one of the field components can propagates up to the Ra…
We have analyzed the solutions to the vector paraxial wave equation in the unbounded uniaxial crystal in the form of the transverse electric (TE) and transverse magnetic (TM) mode beams transporting the fractional optical vortices in the circularly polarized components. We revealed that the TE and TM beams have asymmetric structure in distributing the local elliptic polarization over the beam cross-section and form two sets of singular beams depending on the real or imaginary value of the free K parameter. We found that the fractional optical vortex born in the left handed circularly polarized…
Spatiotemporal optical vortices with controllable radial and azimuthal quantum numbers
本文理论并实验研究具有可控径向与方位角量子数的STLG波包，揭示其复合横向OAM，并利用强时空像散实现与STHG波包的模式转换及模式识别。
As a new degree of freedom for optical manipulation, recently spatiotemporal optical vortices (STOVs) carrying transverse orbital angular momentums have been experimentally demonstrated with pulse shapers. Here a spatiotemporal differentiator is proposed to generate STOVs with transverse orbital angular momentum. In order to create phase singularity in the spatiotemporal domain, the spatiotemporal differentiator is designed by breaking spatial mirror symmetry. In contrast to pulse shapers, the device proposed here is a simple one-dimensional periodic nanostructure and thus it is much more comp…
Optical vortices, as a kind of structured beam with helical phase wavefronts and doughnut shape intensity distribution, have been used for fabricating chiral structures in metal and spiral patterns in anisotropic polarization-dependent azobenzene polymer. However, in isotropic polymer, the fabricated microstructures are typically confined to non-chiral cylindrical geometry due to two-dimensional doughnut intensity profile of optical vortices. Here we develop a powerful strategy for realizing chiral microstructures in isotropic material by coaxial interference of a vortex beam and a plane wave,…
Realizing single light bullets and vortices that are stable in high dimensions is a long-standing goal in the study of nonlinear optical physics. On the other hand, the storage and retrieval of such stable high dimensional optical pulses may offer a variety of applications. Here we present a scheme to generate such optical pulses in a cold Rydberg atomic gas. By virtue of electromagnetically induced transparency, strong, long-range atom-atom interaction in Rydberg states is mapped to light fields, resulting in a giant, fast-responding nonlocal Kerr nonlinearity and the formation of light bulle…
Formation of optical vortices using coherent laser beam arrays
提出了一种利用多光束相干叠加产生涡旋光束的新方案。根据广义惠更斯-菲涅耳衍射积分，导出了相干径向激光列阵的一般传输表达式。在此基础上，分析了小光束数目、小光束间距和拓扑荷数对光束强度和相位分布的影响。模拟结果表明，具有良好初始相位分布的相干径向激光阵列在自由空间中传输时，由于各子光束的干涉和叠加效应，可以有效地形成和产生光学涡旋。在聚焦系统中，聚焦面附近的合成光束具有很强的旋转效应，并具有位相螺旋性。
We show how the phase profile of a distribution of topological charges (TC) of an optical vortex (OV) can be described by a potential analogous to the Coulomb's potential for a distribution of electric charges in two-dimensional electrostatics. From what we call the Topological Potential (TP), the properties of TC multipoles and a 2D radial distribution were analyzed. The TC multipoles have a transverse profile that is topologically stable under propagation and may be exploited in optical communications; on the other hand, the 2D distributions can be used to tune the transverse forces in optic…
Based on the Kirchhoff-Fresnel approximation, we consider behavior of the optical vortices (OV) upon propagation of the diffracted Laguerre-Gaussian (LG) beams with topological charge |m| = 1, 2. Under conditions of weak diffraction perturbation (i.e. the diffraction obstacle covers only the far transverse periphery of the incident LG beam), the OVs describe almost perfect 3D spirals within the diffracted beam body, which is an impressive demonstration of the helical nature of an OV beam. The far-field OV positions within the diffracted beam cross section depend on the wavefront curvature of t…
Perfect optical vortex (POV) is a type of vortex beam with an infinite thin ring and a fixed radius independent of its topological charge. Here we propose the concept of generalized perfect optical vortex along arbitrary curves beyond the regular shapes of circle and ellipse. Generalized perfect optical vortices also share the similar properties as POVs, such as defined only along infinite thin curves and owning topological charges independent of scales. Notably, they naturally degenerate to the POVs and elliptic POVs along circles and ellipses, respectively. We also experimentally generated t…
In the last two decades, optical vortices carried by twisted light wavefronts have attracted a great deal of interest, providing not only new physical insights into light-matter interactions, but also a transformative platform for boosting optical information capacity. Meanwhile, advances in nanoscience and nanotechnology lead to the emerging field of nanophotonics, offering an unprecedented level of light manipulation via nanostructured materials and devices. Many exciting ideas and concepts come up when optical vortices meet nanophotonic devices. Here, we provide a mini review on recent achi…
Focusing and correlation properties of white-light optical vortices
我们通过将圆偏振的部分非相干光通过单轴晶体来产生双电荷白光光学涡旋。我们发现，产生的多色涡旋是结构稳定的，它们的相关特性可以通过光束聚焦改变，导致涡核可见度的变化。
Fractional-order vector vortex beams are recently demonstrated to be new carriers of fractional-strength optical vortices. However, why can those new vortex beams formed by the combination of both unstable states propagate stably in free space? Here, we solve this scientific problem by revealing the physical essence of propagable fractional-strength optical vortices in free space.Three new understandings regarding those peculiar vortex beams are therefore proposed, namely Abbe diffraction limit, phase evolution of vortex beam, and phase binary time vector property.For the first one, owing to A…
Optical Vortex Ladder via Sisyphus Pumping of Pseudospin
针对任意轨道角动量光学涡旋的可控生成难题，提出基于光子石墨烯赝自旋西西弗斯泵浦的光学涡旋阶梯概念，可无衍射可调谐生成任意阶涡旋，为拓扑奇点的光束调控应用开辟新路径。
The generation of optical beams with multiple, mutually-coherent orbital-angular-momentum (OAM) modes using phase gratings is analyzed from the perspective of energy distribution and radial mode composition. We show that phase gratings designed with equally-weighted Laguerre-Gauss (LG) modes will generate beams with uneven energy distribution among OAM components. This unwanted outcome cannot be corrected by adjusting the width of the illuminating beam. We propose a way to design phase gratings that will produce a uniform energy distribution among the constituent OAM states after illumination,…
Propagation of space-time optical vortices in multimode fibers
本文研究了时空光学涡旋在多模光纤中的传播，分析了模式耦合、截断效应及线性与非线性传播特性，揭示了其在多模非线性光学领域的应用潜力。
We demonstrate the generation of far-field propagating optical beams with a desired orbital angular momentum by using a smooth optical mode transformation between a plasmonic vortex and free space Laguerre-Gaussian modes. This is obtained by means of an adiabatically tapered gold tip surrounded by a spiral slit. The proposed physical model, backed up by the numerical study, brings about an optimized structure which is fabricated by using highly reproducible secondary electron lithography technique. Optical measurements of the structure excellently agree with the theoretically predicted far-fie…
Controlled generation of high-harmonic spatiotemporal optical vortices
本文通过高次谐波产生技术，将定制脉冲整形器产生的红外时空光学涡旋脉冲上转换至极紫外频段，明确其拓扑电荷规律并实现可控产生，为相关光谱学研究提供新工具。
Controllable perfect spatiotemporal optical vortices
针对常规时空光学涡旋强度分布半径随拓扑荷变化的局限，提出完美时空光学涡旋概念，其强度几乎不受拓扑荷影响，可通过时空傅里叶变换生成且模式能经方位角相位调制自由调控，实验验证了该波包的生成，拓展了相关研究与应用场景。
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